Torsen T2R Spinning Inside Tire

[b302]

I am the Boss owner in the OP's post, thanks everyone for the helpful replies! I talked to some people today about this issue and I'm not yet 100 percent convinced it is a diff issue. If anything it seems like my outside/unloaded tire is spinning, though from what the OP describes we have very similar symptoms. I am running 500 lb front and I believe 350 lb rear springs. The issue also only appears when I run Pirelli takeoffs, it did not happen on the factory suspension and v710's, and does not happen with this current setup on crappy street tires.

 

[2008 V6]

3.5:1 bias ratio, on Eaton's website:

http://www.eaton.com/Eaton/ProductsServices/Automotive/DifferentialsLockingDifferentials/PCT_317264

Thanks - 3.5 - 1.0

 

[Arustik]

I stand corrected. Looks like the notion of a preloaded T2R of any kind may be a remnant of the past, and for GM guys only. I know of at least one local GM guy who has clutches in his T2R but the car was put together like 10 years ago. At this point some T2R's might at most have preload springs in them but are just as vulnerable to lifting a wheel and spinning the inside tire.

From the sound of it OP's car is a daily driver or at least street-driven, otherwise a Detroit Locker might really be the hot ticket. I'm kind of in the same boat, and the Truetrac is just not quite doing it for me on R-comps. We will experiment with the Whiteline rear bar settings, but I have a sneaking suspicion the car won't like anything other than full soft or completely detached. Upping the spring rates and setting the front bar stiffer will probably help as well.

I ended up just going with a T2-R. To be installed soon and will give you guys my feedback. My friend in the Boss 302 said he doesn't think it's his diff that's causing the inner tire to spin - he thinks it's either the beading of the tires (I don't) or car setup.

As for my car it's not a daily at all anymore. I'd say it's a 90% racer and 10% daily

Yes, you can. In fact the first generation HWMMV had Torsens front and rear and you had to apply the brakes and gas together if you had a wheel airborne. The idea is to eliminate that "open diff" condition without having the driver make the corrective measure since generally applying brakes mid corner while trying to accelerate is counter intuitive and difficult to do.

Personally, if you have a Torsen or other gear diff and are seeing inside wheel spin then I would spend a lot of time focusing on car setup and run less bar and more spring out back or more spring up front to keep more weight on that inside rear.

I'm pulling the rear bar, stiffening up the front sway a bit and going with a Torsen, hope this solves the issue here.

Or left-foot brake better

Not sure about this.

Left foot braking while accelerating is a horrible idea... fix the suspension setup and power out of the corner correctly.



Higher bias ratio with the clutch packs. My understanding is that the difference between the T2 and the T2R is that the T2R has a different set of metal "wear pucks" that are more aggressively textured and sit in the pockets for the worm gears and provide the higher bias ratio. That does eventually wear out.

No idea if that is true though as I haven't had a T2R in front of me, let alone apart and in front of me.

Agree on no LFB while accelerating hard, but moderate throttle while LFB is correct and can be fast as hell such as in a slalom .

You generally aren't left foot braking when you are trying to accelerate out of a corner where most of your inside wheel spin would occur on a Torsen diff. Just saying!

Correct

 

[Arustik]

I am the Boss owner in the OP's post, thanks everyone for the helpful replies! I talked to some people today about this issue and I'm not yet 100 percent convinced it is a diff issue. If anything it seems like my outside/unloaded tire is spinning, though from what the OP describes we have very similar symptoms. I am running 500 lb front and I believe 350 lb rear springs. The issue also only appears when I run Pirelli takeoffs, it did not happen on the factory suspension and v710's, and does not happen with this current setup on crappy street tires.

Thanks for chiming in. We need to figure this out.

 

[NoTicket]

500/350 is not enough front bias depending on the arb you are running. Have you tried taking out the rear bar? You are running spring rates in the rear that I have only seen Terry Fair use on his mustang that was running 800lbs/in in the front.

 

[Arustik]

500/350 is not enough front bias depending on the arb you are running. Have you tried taking out the rear bar? You are running spring rates in the rear that I have only seen Terry Fair use on his mustang that was running 800lbs/in in the front.

D, I actually went from the 350 (too stiff) in the rear back down to 250. I may try to go with 650 front and 250 rear next season.

 

[Dubstep Shep]

Has anyone actually ever measured the bias on these diffs?

Or does anyone have one outside their car they'd be interested in trying to measure?

It would interesting to see how a test stacked up to the manufacturer claims, and you could try different things to try and change the bias ratio to your advantage.

 

[Sky Render]

Has anyone actually ever measured the bias on these diffs?

Or does anyone have one outside their car they'd be interested in trying to measure?

It would interesting to see how a test stacked up to the manufacturer claims, and you could try different things to try and change the bias ratio to your advantage.

I'm curious how you would test that.

Wish I would've known that sooner; I wouldn't have thrown my busted old Trac-Lok away.

 

[Dubstep Shep]

I'm curious how you would test that.

Wish I would've known that sooner; I wouldn't have thrown my busted old Trac-Lok away.

Well you'd have to have some sort of case to test it in that you could fill with gear oil.

Beyond that, testing would be fairly simple.

Immobilize the diff using the ring gear bolt holes.
Set up the diff with whatever fluid you want.
Put a mock up axle in one side that has a torque sensor on it and lock the end of it to something solid.
Neither this 1st axle nor the diff should turn at all.
Put another axle with a torque sensor on the other side.
Place an arm on this second axle and begin to apply torque.

Ideally what you would see is that one of the torques read is exactly the torque from the other axle multiplied by the bias ratio, and that the torque on the ring gear mount is the sum of the torques from the two axles.

That sound about right to you guys?

 

[Sky Render]

No, it doesn't, because you're immobilizing one axle. A limited-slip is supposed to operate when one wheel is slipping (reduced traction) not in the air (no traction) or immobilized (again, no traction).

 

[Dubstep Shep]

No, it doesn't, because you're immobilizing one axle. A limited-slip is supposed to operate when one wheel is slipping (reduced traction) not in the air (no traction) or immobilized (again, no traction).

If the axle is immobilized, that would correspond to absolute traction, not zero traction.

 

[Sky Render]

If the axle is immobilized, that would correspond to absolute traction, not zero traction.

What? No it wouldn't, because the axle couldn't even move, unless I'm misunderstanding what you're saying.

And when does "absolute traction" exist? Never. The best way to test it would be a torque sensor (like AEM's) on the driveshaft and on both axles. Then drive the snot out of it.

Sent from my toilet using Tapatalk

 

[Dubstep Shep]

What? No it wouldn't, because the axle couldn't even move, unless I'm misunderstanding what you're saying.

And when does "absolute traction" exist? Never. The best way to test it would be a torque sensor (like AEM's) on the driveshaft and on both axles. Then drive the snot out of it.

Sent from my toilet using Tapatalk

Not exactly...

The purpose of this setup is to test the bias ratio of the diff, or how much torque the diff will transfer to each one of the axles.

For that experiment to work, the axles must simulate traction. If there is no resistance on one axle, the diff will simply default to an open diff and allow that axle to spin, even if the diff is held in position.

Similarly, if the diff is allowed to spin and one axle is fixed, the diff will essentially be acting as an open diff.

Therefore there must be resistance on both axles for the diff to actually work. The diff is, after all, a "torque sensing" differential. In order for it to transfer torque to one side over another, the other side must have some opposing torque, i.e. traction. If there is zero torque resistance on one axle, that axle will receive all the power, i.e. open diff condition.


And absolute traction never exists? So you spin your wheels everywhere you go no matter what? Man, I bet that's fantastic for your tires.

 

[Whiskey11]

 

[Sky Render]

Not exactly...

The purpose of this setup is to test the bias ratio of the diff, or how much torque the diff will transfer to each one of the axles.

For that experiment to work, the axles must simulate traction. If there is no resistance on one axle, the diff will simply default to an open diff and allow that axle to spin, even if the diff is held in position.

Similarly, if the diff is allowed to spin and one axle is fixed, the diff will essentially be acting as an open diff.

Therefore there must be resistance on both axles for the diff to actually work. The diff is, after all, a "torque sensing" differential. In order for it to transfer torque to one side over another, the other side must have some opposing torque, i.e. traction. If there is zero torque resistance on one axle, that axle will receive all the power, i.e. open diff condition.


And absolute traction never exists? So you spin your wheels everywhere you go no matter what? Man, I bet that's fantastic for your tires.

Yes, all tires slip at least a little, all the time. I thought you were a mechanical engineer?

But I fail to see how keeping one axle from moving at all replicates traction. Maybe it's because I got a degree in electrical engineering instead.

There you go.

 

[Dubstep Shep]

Yes, all tires slip at least a little, all the time. I thought you were a mechanical engineer?

Not sure where you heard that... On a molecular level, I suppose you may have something. Friction is simple the molecular hills and valleys of two objects hitting each other as they go by. In that sense sure, some molecules won't lock together, they'll slide, so you have dynamic friction on those particular molecules.

However, there's a pretty large difference between traction with a tire that's in the static friction zone and a tire that's in the dynamic friction zone. When you "lose" traction, you're entering the dynamic friction zone.

It is possible for a tire to switch between dynamic and static friction so quickly that it's nearly in both states simultaneously. This is because of how tires deform under load and so forth. In that circumstance, you could say that the tire was in both.

But if you're nowhere near losing traction, you're in the static friction zone for that tire.

But I fail to see how keeping one axle from moving at all replicates traction. Maybe it's because I got a degree in electrical engineering instead.

So think of it like this.

The purpose of a differential is to "differentiate" the speeds of your two axles, allowing you to turn without breaking one of your tires lose. If you've never driven a vehicle that has no differential, I invite you to try it.

Unfortunately, because the differential provides a means where the axles can spin at different rates, it also means any loss in resistance on either axle will immediately cause the other axle to receive less torque proportional to that loss in resistance. This is known as the "open diff" condition, because it the axle with the loss in resistance now receives more torque, similar to how a lower resistance wire will flow more current than a higher resistance wire.

The purpose of Torsen, limited slip, and any other differential like these is to allow the wheels to rotate at different speeds during Norman cornering, but to maximize traction by not transferring all power to the wheel with less resistance.

In a Torsen diff, this is accomplished by interlocking gears that can "sense" the torque resistance in the axles. Whichever axle has more resistance receives more power. The bias ratio is the measurement of the maximum ratio of torque in one wheel to the other. If you had an infinite bias ratio, the differential would never default to open diff condition. The way this measurement system works is by exerting a torque on one exile while holding the diff on a resistance type mount, creating a situation where, if the other axle is held, the torque you apply on one axle should equal the torque on the fixed axle divided by the bias ratio. The torque measured on the diff should be the sum of the axle torques.

It's similar to the test setup, except it tests the differential statically, without the need for rotation or centrifugal forces.

 

[NoTicket]

... So much useful information is developing here.